1. Field of the Invention
This invention relates to an adhesive composition. More particularly, it relates to an adhesive composition which possesses a particularly excellent rust-proofing property and suits lamination of a polyvinyl fluoride film and a metallic sheet.
2. Description of the Prior Art
In recent years, laminated sheets of polyvinyl fluoride film excelling in stability to resist weather conditions, resist abrasion, and resist solvents have been attracting attention as materials for wallboards and materials for roof plates. The polyvinyl fluoride film is marketed by E. I. Du Pont de Nemours & Co., Inc. under the trademark designation of "Teddler". The Teddler produced in the form of film or sheet is superposed on metallic sheets and the resulting laminated sheets are used as building materials. The adhesive agent which is used for the lamination of this nature must fulfil the requirement that it should possess high adhesive strength, high cohesive strength, rich stability to resist hydrolysis, high resistance to weather conditions, and a rust-proofing property.
If the adhesive agent fails to fulfil the aforementioned requirement, the polyvinyl fluoride film cannot manifest its characteristics fully because the produced laminated sheet is susceptible to separation of component layers and the portions of the component layers joined by adhesion are liable to deterioration. As adhesive agents suitable for lamination of Teddler, those proposed by the same U.S. firm in Japanese Patent Publications SHO No. 38(1963)-18,530 and SHO No. 38(1963)-26,763 and U.S. Pat. No. 3,228,823 have been known to the art. These adhesive agents are produced by copolymerizing several methacrylates with a monomer containing an epoxy group and causing gaseous ammonia or primary monoamine to react upon the resulting polymers. These adhesive agents, therefore, are made of acrylic polymers possessing an amino group or imino group in the side chains thereof.
Meanwhile, the Teddler film to be joined by adhesion has the surface thereof has undergone a special surface treatment as disclosed in Japanese Patent Publication SHO No. 38(1963)-18,530 and U.S. Pat. No. 3,228,823. It is generally held that an adhesive agent which has as a main component thereof an acrylic polymer containing an amino group or imino group in the side chain thereof as disclosed in the aforementioned patent publications provides effective adhesion of the Teddler film and, therefore, proves satisfactory from the practical point of view.
The aforementioned acrylic polymer is a polymer possessing a group represented, for example, by the following formula: ##STR2## wherein Z stands for an aliphatic hydrocarbon residue of 2 or 3 carbon atoms, R.sup.1 for hydrogen atom or an alkyl group of 1 to 8 carbon atoms, R.sup.2 for hydrogen atom, a hydroxyl group, or an alkyl group of 1 to 8 carbon atoms, and R.sup.3 for hydrogen atom or an alkyl group of 1 to 8 carbon atoms. It is obtained by causing an amine to react on a vinyl polymer such as glycidyl methacrylate or causing an imine compound to react on a vinyl polymer possessing a carboxyl group.
Since the laminated products of Teddler film and metallic sheets find utility mainly in outdoor applications, they require the rust-proofing property all the more (for example, edge portions or portions sustaining damge are susceptible to loss of adhesive strength due to corrosion) when they are used in districts with climates of high temperature and high humidity, or districts bordering the sea and tending to suffer from the damage done by the briny spray. Generally, the adhesive agent must exhibit an outstanding performance such as in adhesiveness, resistance to briny spray, and resistance to boiling water to corrosive metals such as, for example, substrates of cooled steel sheets, galvanized steel sheets, and aluminum sheets.
The qualities exhibited by the conventional adhesive agent, however, are not fully satisfactory.
An object of this invention, therefore, is to provide a novel adhesive composition.
Another object of this invention is to provide an adhesive composition suitable for lamination of a polyvinyl fluoride film and a metallic sheet.
A further object of this invention is to provide an adhesive composition capable of manifesting a well-balanced performance in adhesiveness, resistance to boiling water, resistance to moisture, corrosionproofness, and weatherability.